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 A182594 Number of prime factors of form cn+1 for numbers 7^n-1 0

%I

%S 1,1,2,1,2,2,1,3,3,2,2,1,4,2,3,2,4,2,3,1,4,3,4,3,3,4,4,3,3,3,2,4,3,3,

%T 3,3,4,4,5,3,4,2,4,2,4,2,3,4,4,5,5,3,5,1,6,3,4,4,5,4,6,2,3,6,6,4,6,3,

%U 8,2,5,5,5,3,2,3,7,2,5

%N Number of prime factors of form cn+1 for numbers 7^n-1

%H S. Mustonen, <a href="http://www.survo.fi/papers/MustonenPrimes.pdf">On prime factors of numbers m^n+-1</a>

%e For n=9, 7^n-1=40353606=2*3^3*19*37*1063 has three prime factors of form, namely 19=2n+1, 37=6n+1, 1063=118n+1. Thus a(9)=3.

%t m = 7; n = 2; nmax = 80;

%t While[n <= nmax, {l = FactorInteger[m^n - 1]; s = 0;

%t For[i = 1, i <= Length[l],

%t i++, {p = l[[i, 1]];

%t If[IntegerQ[(p - 1)/n] == True, s = s + l[[i, 2]]];}];

%t a[n] = s;} n++;];

%t Table[a[n], {n, 2, nmax}]

%K nonn

%O 2,3

%A _Seppo Mustonen_, Nov 22 2010

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Last modified February 25 05:11 EST 2020. Contains 332217 sequences. (Running on oeis4.)